A lectin from the green seaweed Caulerpa cupressoides reduces mechanical hyper-nociception and inflammation in the rat temporomandibular joint during zymosan-induced arthritis

Seaweed lectins have been widely investigated as anti-nociceptive and anti-inflammatory agents. This study analyzed the anti-nociceptive and anti-inflammatory responses of a lectin from the green seaweed Caulerpa cupressoides (CcL) on zymosan-induced arthritis of the rat temporomandibular joint (TMJ). Rats received i.v. CcL 30 min prior to injection of zymosan (2 mg/art.) or 0.9% saline into the left TMJ. Mechanical hyper-nociception was measured by the electronic von Frey method at baseline and 4 h after zymosan injection. Animals were euthanized 6 h after zymosan injection and the synovial fluid was collected for leukocyte counting and myeloperoxidase activity assessment. Other animals were treated with ZnPP-IX (3 mg/kg; s.c.), a specific heme oxygenase-1 pathway inhibitor, and naloxone (10 μg/art.), a nonselective opioid receptor antagonist. TMJ tissues were excised to perform histopathological and immunohistochemistry analyses. CcL (0.1, 1 or 10 mg/kg) significantly reduced zymosan-induced hyper-nociception (81, 83 and 89.5%, respectively) and inhibited the leukocyte influx (77.3, 80.7 and 98.5%, respectively) compared with the zymosan-only group, as confirmed by myeloperoxidase activity; however, treatment with naloxone or ZnPP-IX did not revert the effects of CcL (10 mg/kg), suggesting that the naloxone-sensitive opioid and heme oxygenase-1 pathways are not involved. CcL also reduced the leukocyte influx and the expression of IL-1β and TNF-α in the TMJ, based on histopathological and immunohistochemistry analyses, respectively. Therefore, CcL reduces TMJ hyper-nociception and inflammation with a mechanism that is partially dependent on TNF-α and IL-1β inhibition. CcL reveals a potentially valuable alternative tool for future studies of TMJ disorders.